According to statistics, accidents involving falls from heights are the leading cause of severe injuries and deaths in the workplace. Approximately one in every seven work-related fatalities is caused by falling from heights. Recent studies point to the lack of appropriate working conditions as the main factor for the increase in these numbers.
In March 2012, Edict 313 from the Secretariat of Labor Inspection (SIT) was published in the Official Federal Gazette, approving Regulatory Standard [Norma Regulamentadora] no. 35—Work at Heights. This new NR establishes the minimum requirements and the protection measures involving the planning, organization and execution of work at heights, so as to guarantee the safety and health of workers directly or indirectly involved in this type of activity.
Various systems are available in the market. These differ significantly in design and application. Characteristics of safety, functions, handling and ease of use must be evaluated. Besides this, durability, maintenance costs and long-term value should be considered to select the best system. In all cases, fall-arresting systems should be designed for each specific application. This will minimize the risk of falling from heights and maximize the efficiency of the work to be performed.
Lifeline systems, as they are known today, are regulated by NR 18 and involve installation of a cable or rope connected to a safety harness to secure the worker, and anchor points, with the objective of allowing people to work at heights safely.
There are two types of lifelines according to the time frame of use. The most often utilized are provisional or temporary, which are assembled, used and disassembled in the phase of the work project in which they are necessary. And there are also fixed ones that are installed and remain during the entire project.
The provisional horizontal lifeline is a means to anchor against falls and is normally composed of a metal cable, generally stored on a drum with a retraction and locking mechanism, as well as a free end with a means of attachment, in the form of a snap hook or similar device. The system as a whole is designed to adjust to the structures and anchor points, which are demonstrably able to withstand the forces exerted by a fall. For example, the lifeline has at least two anchor points, preferably in the form of a post or brace, made of metal, wood or other material, which are attached to the lifeline.
These systems are produced for specific uses. The worker can use a safety belt and a fastening component (for example, a baldric with energy absorber or a retractable fall arrester) that connects to the lifeline by a trolley wheel of shuttle, able to pass freely through intermediate supports. Therefore, the worker can move horizontally with total safety, because he is connected to the system at all times.
However, many of these systems present some insecure points, because as is known to practitioners, in a possible fall of a worker connected to a horizontal lifeline, the forces generated at the ends of this lifeline are amplified and can damage the support structures of the system and impair the worker's safety. This effect can be multiplied when multiple workers use the same lifeline.
The drawbacks of the current systems are concentrated, more specifically, in the support points, such as anchor posts and the lifeline drum. The anchor posts are generally made in the form of steel tubes and are attached with their lower ends driven into the by the fact that the, so as to remain vertical. Many times their length exceeds more than two or three floors of the building under construction, making them hard to transport. Besides this, although these posts generally serve as a means to secure the lifeline, the line is often wound around the post, in direction of the other, where it is also wound or tied, to compose the horizontal lifeline.
Some anchor posts have safety guides or holes through which the lifeline passes. For example, document U.S. Pat. No. 4,037,824 (WHITMER) contemplates an anchor post provided with two small parts forming an arch, which together form a “U” fastened to the top of said anchor post. In turn, document U.S. Pat. No. 2,706,662 (DOYES) contemplates at least one “C” link welded to the side of a post.
Therefore, as seen, the “U” links commonly used are not sufficiently closed, and thus do not prevent the detachment of the lifeline when a high force is placed on it. In turn, the “C” link welded to the post means that the lifeline can only be passed though the link from its free end. If there is a need to attach a portion of the lifeline other than its free end, the worker must splice it to the post, not generating any safety.
Another drawback is the fact that the retractable lifeline drums are fastened to these types of links from the anchor posts. For example, the document from the state of the art US2008035423 (D. B. Ind.) demonstrates that the guide of the retractable drum mechanism is mounted on a “C” link welded to the anchor post, so that said mechanism can move freely, according to the movement imposed by the worker on the lifeline, which even when stretched can present considerable swinging motion, fruit of the freedom of movement of the drum in relation to the safety point of the anchor post. This swinging of the lifeline generates severe instability for the worker.
Therefore, it is clear that the current technical state of horizontal lifeline systems, even though in constant evolution in response to current technical standards, requires improvements related to the anchoring devices, mainly aimed at safety of the workers. However, these improvements should not make the work more costly.